100% did not.intend that: I assume that it is an algorithmic quirk when requesting a group of people with the same description, cut and paste. It was notable that I got diverse clothing when I stipulated "rainbow."
It's sometimes called the "twin effect" where all your characters end up being clone. The more there are, the more often it occurs. I think it's pretty strong with Dall-E because they obviously tried hard (and succeeded...) to avoid concept bleeding (that's when you ask for a fighter with a green sword and black armor and you get random green armor pieces). If the prompt we type for a generic member of a group is reapplied for each, similarities are bound to happen more often.